Input devices including proximity sensor devices (also commonly referred to as touchpads or touch sensor devices) are widely used in a variety of electronic systems. A proximity sensor device typically includes a sensing region, often demarked by an input surface, in which the proximity sensor device determines the presence, location, and/or motion of one or more input objects. Proximity sensor devices may be used to provide interfaces for the electronic system. For example, proximity sensor devices are often used as input devices for larger computing systems (such as opaque touchpads integrated in, or peripheral to, notebook or desktop computers). Proximity sensor devices are also often used in smaller computing systems (such as touch screens integrated in cellular phones).
Some input devices also have the ability to detect forces applied to an input surface. For example, one or more force sensors positioned beneath the input surface may detect the amount of force exerted on the input surface based, at least in part, on a movement or deflection of the input surface under the applied force. A force sensing resistor (FSR) is a specific type of force sensor that acts as variable resistor when a force or pressure is exerted on the sensors. For example, the resistance of the FSR may be inversely related to the amount of pressure exerted, such that the resistance of the FSR may decrease as greater pressure is exerted on the FSR. Thus, the input device may measure the resistance of the FSR to determine the amount of force applied on the input surface.
In its quiescent state (e.g., when no force or pressure is applied), an FSR acts as an open circuit. The FSR functions as a resistor only after a threshold amount of pressure is applied to the input surface (e.g., causing an active area of the FSR to come into contact with a resistive substrate). Thus, light taps and/or touches on the input surface may not trigger a change in the resistance of the FSR. However, it may be desirable nonetheless to detect such light taps and/or touches as user inputs.